Bulletin of the American Physical Society
2007 APS March Meeting
Volume 52, Number 1
Monday–Friday, March 5–9, 2007; Denver, Colorado
Session X32: Quasi-One-Dimensional Quantum Gases |
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Sponsoring Units: DAMOP Chair: Ana Maria Rey, Harvard-Smithsonian Center for Astrophysics/ITAMP Room: Colorado Convention Center 402 |
Friday, March 9, 2007 8:00AM - 8:12AM |
X32.00001: Decoherence dynamics in low-dimensional cold atoms condensates Anton Burkov, Mikhail Lukin, Eugene Demler We report on a theoretical study of the dynamics of decoherence of a matter-wave interferometer, consisting of a pair of low-dimensional cold atoms condensates. We identify two distinct regimes in the time dependence of the coherence factor of the interferometer: quantum and classical. Explicit analytical results are obtained in both regimes. In particular, in two-dimensional (2D) condensates in the classical (long time) regime, we find that the dynamics of decoherence is universal, exhibiting a power-law decay with an exponent proportional to the ratio of the temperature to the Kosterlitz-Thouless temperature of a single 2D condensate. In the one-dimensional (1D) case we find a nonanalytic time dependence of decoherence,which is a consequence of the nonhydrodynamic nature of damping in 1D liquids. [Preview Abstract] |
Friday, March 9, 2007 8:12AM - 8:24AM |
X32.00002: Crossover to a quasi-condensate in a weakly interacting trapped 1D Bose gas Karen Kheruntsyan, Isabelle Bouchoule, Gora Shlyapnikov One-dimensional (1D) Bose gases are remarkably rich physical systems exhibiting properties not encountered in 2D or 3D. Here we study the exactly solvable 1D model of bosons interacting via a repulsive delta-function potential. Specifically, we discuss the system in the context of a harmonically trapped, weakly interacting 1D Bose gas at ultra-low temperatures and analyze the transition from a fully decoherent regime to a coherent, quasi-condensate regime. By finding the characteristic critical temperature and atom number that depend explicitly on the interaction strength and the trap frequency, we specify the conditions for identifying this transition as an interaction-induced crossover. We contrast this to the finite-size Bose-Einstein condensation (BEC) phenomenon studied previously in the context of an ideal trapped 1D Bose gas. We predict that for sufficiently weak confinement one expects to observe the interaction-induced crossover scenario, rather than the finite-size BEC. The situation is reversed for strong confinement. We identify typical experimental parameters that enable the realization of either of these two competing scenarios. [Preview Abstract] |
Friday, March 9, 2007 8:24AM - 8:36AM |
X32.00003: Quantum Monte Carlo study of a 1D phase-fluctuating condensate Charlotte Gils, Lode Pollet, Alice Vernier, Frederic Hebert, George Batrouni, Matthias Troyer Starting from a microscopic description, we numerically investigate the low temperature behaviour of a trapped one dimensional Bose gas with repulsive interactions. For a sufficient number of particles and weak interactions, we identify a pronounced quasicondensate regime in temperature, where density fluctuations are negligible while phase fluctuations are considerable. In the weakly interacting limit, we find good agreement of our results with those obtained using a mean-field approximation. In addition, we study the system in parameter regimes which are beyond the accessibility of mean-field approaches. A phase-fluctuating condensate exists also in these cases, but phase-correlation properties are qualitatively different. [Preview Abstract] |
Friday, March 9, 2007 8:36AM - 8:48AM |
X32.00004: Spin dynamics in the two-component strongly repulsive 1D Bose gas Mikhail Zvonarev, Thierry Giamarchi, Vadim Cheianov We investigate spin diffusion in the two-component one- dimensional Bose gas in the limit of strong repulsion. While the spectrum of charge excitations can be linearized in such a system, it remains quadratic in the spin sector, and the Luttinger Liquid description is not applicable. However, we showed that dynamical Green's functions of the system can still be found by using a mapping onto an effective spinless model. In this way we get an exact analytic expression for the one-particle and spin-spin Green's functions and found an anomalously low spin-diffusion rate. [Preview Abstract] |
Friday, March 9, 2007 8:48AM - 9:00AM |
X32.00005: Dynamical correlation functions of the 1D Bose gas (Lieb Liniger model) Jean-Sebastien Caux, Pasquale Calabrese The momentum- and frequency-dependent correlation functions (one-body and density-density) of the one-dimensional interacting Bose gas (Lieb-Liniger model) are obtained for any value (repulsive or attractive) of the interaction parameter. In the repulsive regime, we use the Algebraic Bethe Ansatz and the ABACUS method to reconstruct the correlators to high accuracy for systems with finite but large numbers of particles. For attractive interactions, the correlations are computed analytically. Our results are discussed, with particular emphasis on their applications to quasi-one-dimensional atomic gases. [Preview Abstract] |
Friday, March 9, 2007 9:00AM - 9:12AM |
X32.00006: Full distribution functions of interference contrast in low-dimensional bose gases Adilet Imambekov, Vladimir Gritsev, Eugene Demler We consider interference experiments with two independent low dimensional bose condensates. Full distribution function of fringe visibilities is determined by higher order correlation functions within individual condensates and contains non trivial information about quantum and thermal fluctuations in the system. We develop a general method for calculating distribution functions of the interference amplitude and apply it to one and two dimensional condensates both at zero and finite temperatures. [Preview Abstract] |
Friday, March 9, 2007 9:12AM - 9:24AM |
X32.00007: Strongly correlated bosons on optical superlattices: Dynamics and relaxation in the superfluid and insulating regimes Marcos Rigol, Maxim Olshanii, Alejandro Muramatsu We study the nonequilibrium dynamics of hard-core bosons (HCB's) on one-dimensional lattices. The dynamics is analyzed after a sudden switch-on or switch-off of a superlattice potential, which can bring the system into insulating or superfluid phases, respectively. A collapse and revival of the zero-momentum peak can be seen in the first case. We study in detail the relaxation of these integrable systems towards equilibrium. We show that after relaxation time averages of physical observables, like the momentum distribution function, can be predicted by means of a generalization of the Gibbs distribution. [M. Rigol, A. Muramatsu, and M. Olshanii, Phys. Rev. A 74, 053616 (2006).] [Preview Abstract] |
Friday, March 9, 2007 9:24AM - 9:36AM |
X32.00008: Spectroscopy and quantum quench dynamics of interacting one-dimensional Bose condensates Vladimir Gritsev, Anatoli Polkovnikov, Eugene Demler We discuss applications of the exact solution of the quantum sine Gordon model to study non equilibrium dynamics of two coupled interacting one dimensional Bose liquids. In particular, we consider a set up in which a sudden quench of the tunneling amplitude introduces oscillations in the relative phase of the two condensates. We demonstrate that the power spectrum of the interference amplitude oscillations should reveal the non trivial excitation spectrum of the quantum sine Gordon model. [Preview Abstract] |
Friday, March 9, 2007 9:36AM - 9:48AM |
X32.00009: Onset of Chaos and Thermalization in a One-Dimensional Bose-Hubbard Lattice in the Mean-Field Regime Douglas Mason, Amy Cassidy, Vanja Dunko, Maxim Olshanii The goal of this work is to identify a Chirikov threshold for the onset of chaos and, beyond the threshold, to study thermalization in a one-dimensional Bose-Hubbard Model. In the mean-field approximation the problem is conceptually close to the one of the beta-f Fermi-Pasta-Ulam model. In the regime of well developed chaos the atomic momentum distribution is shown numerically to converge to the predictions of the grand canonical ensemble, simulated in turn using the Monte Carlo method. We find good agreement between our analytical predictions and the results of our numerical calculations. We discuss the relevance of our results to the recent Newton's Cradle experiments on relaxation of an ensemble of bosonic atoms in a one-dimensional optical trap [T. Kinoshita, T. Wenger, D.S. Weiss, Nature (London) 440, 900 (2006)]. [Preview Abstract] |
Friday, March 9, 2007 9:48AM - 10:00AM |
X32.00010: Dynamics of Bose gases in Y-shaped potential and Andreev-type reflection Akiyuki Tokuno, Masaki Oshikawa, Eugene Demler Recently, guiding of atoms in low-dimensional magnetic traps has been actively studied. While the theory of one-dimensionally trapped atoms has been vigorously studied, much of the dynamical aspects remain unexplored. As a simple yet nontrivial example, we study the real-time dynamics of BEC in the Y-shaped potential. Collective nature of the transport is considered by treating each one-dimensional channel as a Tomonaga-Luttinger liquid. We analytically investigate the reflection and transmission at the center of the potential, for a high-density packet moving from one side to the other sides. Even though we study a system of bosons, we find that the reflection at the center of the potential exhibits an Andeev-type reflection reminiscent of that at a normal-superconductor interface in electron systems. This could be attributed to the fermionic nature of the repulsively interacting Bose systems in one dimension. In addition, we shall also discuss the dynamics in the ring type interferometer which consists of two symmetric Y-junction. [Preview Abstract] |
Friday, March 9, 2007 10:00AM - 10:12AM |
X32.00011: Ultracold bosons in one-dimensional incommensurate superlattices Tommaso Roscilde, Ignacio Cirac Motivated by recent experiments (L. Fallani et al., cond-mat/0603655), we numerically investigate the ground-state properties of strongly interacting ultracold bosons in a one-dimensional quasi-periodic superlattice, modeled by the Bose-Hubbard Hamiltonian in an incommensurate cosine potential. In the weakly interacting regime, the incommensurate potential (IP) is known to lead to Anderson localization when exceeding a given critical strength. We find that strong repulsion, giving rise to a Mott-insulating state for the system without the IP, introduces an extremely rich physical scenario. For repulsion values away from the Tonks limit an IP added to the Mott phase is effectively screened by a fraction of the particles, and drives the system to a superfluid phase for the remaining fraction. For larger IPs, a cascade of incompressible insulating states appears with incommensurate fractional fillings. The change of filling from a state to the next is usually accompanied by significant particle number fluctuations without superfluidity, namely by Bose-glass behavior in narrow parameter ranges. [Preview Abstract] |
Friday, March 9, 2007 10:12AM - 10:24AM |
X32.00012: Damping of condensate oscillations of a trapped Bose condensate in a 1D optical lattice at finite temperatures Emiko Arahata, Tetsuro Nikuni We study Landau damping of dipole oscillations of a Bose condensate in a 1D optical lattice at finite temperatures. Assuming that an additional trap potential is highly anisotropic, in which the radial confinement is much tighter than the axial confinement, we derive a quasi-1D model of the Gross-Pitaeavskii equation and the Bogoliubov equations that include the effect the excitations in the radial direction. We calculate the Landau damping rate and investigate its dependence on the lattice depth, compare our result with the experiental data on collective modes in an optical lattice [F. Ferlaino et. al., Phys. Rev. A 66, 011604(2002)]. [Preview Abstract] |
Friday, March 9, 2007 10:24AM - 10:36AM |
X32.00013: Glassy behavior of Bose-Bose mixtures in one-dimensional optical lattices Ignacio Cirac, Tommaso Roscilde We numerically investigate the properties of strongly repulsive two-boson mixtures in one-dimensional optical lattices, targeting their ground state either by slow cooling from high temperature, or by a slow change in the Hamiltonian parameters starting from the weakly interacting regime. The two bosonic species have very different effective masses, so that the slow bosons can act as an effective potential to the faster ones. When the interspecies repulsion is strong compared with the intraspecies one, a phase-separated ground state is masked by an exponentially large number of metastable \emph{quantum emulsion} states, in which the two species are fragmented into microscopic droplets. The quantum emulsion states can be regarded as the out-of-equilibrium realization of a localization phenomenon, in which each species acts as a random potential to the other one, effectively localizing it. Quantum Monte Carlo investigations reveal an extremely slow relaxation of the system towards equilibrium, typical of a glassy phase. Increasing the intraspecies repulsion for the fast bosons drives them through a quantum phase transition to the superfluid state. [Preview Abstract] |
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